Soil research and earthquake damage prevention

According to postgraduate research student Wang Shengzhe, our understanding of soils’ behaviour is still minimal — and this has to change if we are to prevent the structural damage that can arise from earthquakes.

Wang, from the The University of Sydney’s School of Civil Engineering, was on the ninth floor of a building when a 6.5 magnitude earthquake hit Wellington in 2013, causing the building to sway from side to side. This unnerving experience encouraged him to take up a research degree in soil movement.

“My research examines how soils respond under extreme conditions, such as earthquake, especially when this behaviour is further complicated by the introduction of pore water,” he said.

“I take a small soil sample and place it into a machine. I then subject the sample to a sudden impact. This will allow sensors on the machine to feed me information, which enables me to calculate the soil’s strength, or how much load it can support.”

Wang explained that soil strength can change under impacts from sources including heavy machinery operation, pile driving, explosions or earthquakes. This could have disastrous consequences, such as the manifestation of soil liquefaction — “when wet soils completely lose their strength because of an excessive build-up of water pressure due to the ground shaking”, he said.

According to Wang, the 2011 Christchurch earthquake saw widespread damage result from massive amounts of soil liquefaction. “So it makes sense to avoid constructing buildings on ground with extensively saturated soil prone to liquefaction, or you must have plans for soil remediation such as draining the ground,” he said.

“By adequately understanding the liquefaction potential of soils when planning cities and suburbs, we will know exactly where and where not to construct our facilities and place our most critical infrastructure.”

Wang’s research is claimed to be the first of its kind to systematically investigate the effect of particle size distribution, particle shape and water content on the behaviours of porous media under impact loading. His work will reveal the key factor that controls the particle-water interaction in wet porous media and thus help engineers understand the physics behind the liquefaction of soil in earthquakes.